Polychlorinated Biphenyl Uptake and Transport by Lymph and Plasma Components

Abstract

The uptake and vascular transport of ingested Aroclor 1242, an isomeric mixture of polychlorinated biphenyls (PCB), was investigated in experimental animals. High concentrations of ingested PCB were found in the chylomicron fraction of thoracic duct lymph. When the lymph flow was exteriorized PCB were not subsequently found in the vascular circulation. When lymph was not exteriorized plasma PCB concentrations reached maximal levels 6 hr after ingestion. Less than 1% of total plasma PCB was detected in cellular fractions of blood over a 10-hr period following ingestion. Chylomicrons contained 31% of total plasma PCB 30 min after ingestion, decreasing to less than 6% at 4 hr. A maximum of 10% of plasma PCB at 1 hr, and less than 5% at 6 hr, after ingestion was associated with very low density lipoproteins (VLDL) or low density lipoproteins (LDL). Although PCB enter the vascular circulation with the chylomicron fractions of lymph, delipoproteinated plasma contained 52% of the total PCB in blood collected 30 min after ingestion. This level increased to 78% after 2 hr, and remained constant at about 80% for an additional 8-hr period. High performance liquid chromatographic (HPLC) examinations of delipoproteinated plasma from blood taken 6 hr after PCB ingestion showed elution of greater than 95% of plasma PCB to coincide with the albumin peak. Electrophoretic examinations of delipoproteinated plasma showed the association of PCB with albumin to be noncovalent. The results suggest that apolar PCB are absorbed into intestinal epithelial cells from which they are secreted into the lymphatic drainage sequestered within the apolar core of chylomicrons, that these PCB transit the thoracic duct and enter the vascular circulation within chylomicrons and are metabolized or otherwise released from chylomicrons during hepatic chylomicron clearance, and that resulting PCB or PCB derivatives circulate in association with plasma albumins.